Blade fastening means



Feb. 19, 1957 s. WILDER,-JR

BLADE FASTENING-MEANS Filed July 26, 1951 a z i J v w 2 attorneys nitdStates BLADE FASTENING MEANS Stuart Wilder, J12, Indianapolis, Ind.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Application July 26, 1951, Serial No. 238,756

3 Claims. (Cl. 230-134) This invention relates to blading of a typesuitable for use in elastic fluid machines such as axial-flowcompressors and the like, and, more particularly, to improved fasteningmeans for securing blades in apparatus of this character.

The invention has for its objectives the provision of a simple andinexpensive fastening means which provides an efiicient positive locktor securing a footed blade against movement in its mounting slot andwhich may be readily unlocked to permit blade removal and reinsertion.

The advantages attending the use of liooted blades have long beenrecognized and have resulted in their widespread application. However,as this type of blade can not depend for its retention on the frictionalengagenient between the foot of the blade and the walls of the matingslot wherein it is mounted, there is presented, particularly in the caseof blade carrying members used in gas turbine engines, the problem ofpreventing the blade from rattling and backing out of its slot due tothe relatively high tangential and axial forces exerted on the blade.Various means for overcoming this problem have been proposed, but, asfar as is known, none alfords the simplicity of construction andinstallation, the eflicacy of retention and the versatility ofapplication of the present invention.

As applied to a rooted blade with an enlarged foot having a slide fit ina mating slot contained in a blade cam-yi-ng member, the inventionfeatures the use of a resilient fastening member having ext-endedoutwardlydiverging terminal portions, the fastening member beingdetachably mounted in a groove extending transversely about the bladeroot so as to be positively locked thereon. A relieved or notched areaintermediate the ends of the mating slot forms a transverse recesshaving abutting shoulders in the outer portion, preferably, of both ofthe side walls of the slot. The terminal portions of the fasteningmember are constrained to permit the blade and fastening member to beslidably inserted as a unit into the slot, the terminal portions beingreleased when aligned with the recess in which they are received so asto bear against the abutting shoulders thereof, thereby positivelylocking the fastening member and, hence, the blade against movement inthe slot.

The nature of the invention together with other objects, features, andadvantages thereof will be apparent from the following detaileddescription and accompanying drawings in which:

Fig. l is a fragmentary axial view of a rooted blade fastened in a bladecarrying member in accordance with the present invention, certain partsbeing in section;

Fig. 2 is a transverse sectional view of the structure of Fig. 1 takensubstantially along the plane 22 thereof;

Fig. 3 is a sectional view of the structure of Fig. 1 taken along theplane 3-3 thereof; and

Fig. 4 illustrates a form of blade fastening member in accordance withthe invention.

Referring to the drawings, the blade carrying member illustrated in thefragmentary axial sectional view of Fig. 1 may be, for example, a rotorwheel or a portion of a casing or stator of an axial flow compressor orturbine, the general construction of which is well known to thoseskilled in the art so as not to require description herein. The member10 carries a ring of blades 12 spaced about the periphery of the rim 14in respective ones of a plurality of undercut or dovetail blade mountingslots 16, only one of the blades and slots being shown in the drawings.

For purpose of illustration, the invention is shown ap-. plied to ablade 12 having a curved root 18. The root 18 extends substantially thelength of the chord of the blade and has integrally formed on oppositesides thereof a pair of arcuate ribs 20, 21 (Fig. 2) which form anenlarged or bulbular blade foot 24 that is adapted to be slidablyinserted in the mating slot 16, also of curved form as shown in Fig. 1.The shape of the slot 16 corresponds generally to that out thecross-section of the blade root as shown in Fig. 2 and viewed in plan lrom the surface of the rotor resembles a dumb-bell as shown in Fig. 3.

Because the blade root and slot are figures of revolution, the blade maybe installed in the slot by rotating the blade about an axis 0 normal tothe plane of Fig. 1 when the leading edge 26 of the blade foot 24 isinserted in the trailing edge 28 of the slot 16. The trailing edge 30 ofthe blade fiornrs an effective stop and engages the peripheral surfaceof the rotor rim 14 when the insertion is complete as shown in Figs. 1and 3.

In accordance with the invention, the blade is prevented frcm backingout of its slot and from rattling therein by means of a fastening memberwhich is posi;

tively locked to the blade and in the mating slot 16. The fasteningmember consists of a spring clip or wire snap ring 32 resembling ahairpin with flared or outwardly diverging terminal portions 34, 35 asillustrated in Fig. 4 and is detachably mounted in a grooved recess 38intermediate the leading and trailing edges of the blade extendingtransversely around root portion 18 thereof as illustrated in Figs. 2and 3, whereby the snap ring is positively locked in the grooved recessof the blade. The snap ring conforms generally to the shape of the crosssection of the blade foot 24 and is preferably constructed of aresilient spring wire which may have a circular or other cross section.

In order to lock the fastening member and, therefore, the blade in theblade slot, notches 40 and 41 are provided in the surface of the rotorrim 14 as illustrated in Figs. 2 and 3 extending on both sides andintermediate the ends of the slot 16. The faces of the notches formbearing surfaces for the terminal portions 34, 35 of the snap ring. Theterminal portions of the snap ring are constrained or bent inwardlytowards the surfaces of the blade until the terminal portions 34 and 35are flush with thesides of the blade, as shown by the broken lines X, Xof Fig. 2 to permit the blade and snap ring mounted thereon to beinserted in the blade slot by a circular movernent as described above,the terminal portions being released or relieved from constraint so asto snap-back into substantially their original form and to be receivedin the transverse notches 4d, 41 when the blade is installed inposition, thereby forming a positive lock for the snap ring and theblade. The elongated ends of the snap ring, which extend beyond theupper portion of the slot as shown by the broken lines Y, Y of Fig. 2are then cut off near the surface of the slot. To release or unlock theblade, the terminal portions of the snap ring are gripped together onopposite sides of the blade and freed of the locking notches 4t), 41,whereby the blade and snap ring may be rotatably slid out of the slot.

It is thus seen that the invention affords a simple, efficient andpositive lock for securing a footed blade 3- against movement in itsmounting slot. In accordance with the invention, each blade may beindividually removed or inserted without interference with otherstructures, disassembly of other parts or damage to the parts.

Although the invention has been described in connection with a footedblade having a curved root, the invention is not limited to such a bladebut may 'be readily applied to various forms of blade roots in varioustypes of blade carrying members, thus indicating the versatility of theinvention, a feature not readily afforded by other forms of known bladefastening means.

I claim:

1. In combination, a footed blade, a blade carrying member containing amating undercut slot having a relieved area in the sidewalls thereofintermediate its ends, said blade foot having a groove formed in thesurface thereof and extending thereabout transverse to the longitudinalaxis of the foot, and a releasable spring clip mounted in the groove insaid blade foot, the foot of said blade being received in said matingslot in said blade carrying member with said spring clip mountedthereon, said clip having diverging terminal portions that project abovethe peripheral surface of said blade carrying memher and are received inthe relieved area in the blade carrying member locking the blade and theblade carrying member together, the terminal portions of said clip beingreadily accessible and being movable into the groove in said blade footto unlock the foot of the blade from the blade carrying member and allowseparation of one from the other.

2. In combination, a footed blade having a curved foot, a rotor wheelcontaining a curved undercut mating slot having a transverse notch inthe sidewalls of the slot intermediate its ends, said blade foot havinga groove formed in the surface thereof and extending thereabouttransverse to the longitudinal axis of the foot, and a snapring mountedin said transverse groove on said blade foot, said blade foot beingreceived in said mating slot with said snap-ring mounted thereon, saidsnap-ring having diverging terminal portions which project above theperipheral surface of said blade carrying member and are received insaid transverse notch in the sidewalls of the blade carrying memberlocking the foot of the blade and the blade carrying member together,the said termi' nal portions of the snap-ring being readily accessibleand being movable into the groove in the blade foot to unlock the footof the blade from the blade carrying member and allow separation of onefrom the other.

3. In combination, a supporting member formed with an undercut slothaving a transverse notch in the sidewalls of the slot, 21 supportedmember including a foot formed with a groove in the surface thereoftransverse to the longitudinal axis of the blade foot, and a clipmounted in said groove, said supported member being re ceived in themating slot in said supporting member with said clip mounted on the footthereof, said clip having terminal portions that project above theperipheral surface of said supporting member and are received in saidnotch in said supporting member locking the members together, the saidterminal portions of the clip being readily accessible and being movableinto the groove in the foot of the supported member to unlock themembers and allow separation thereof.

References Cited in the file of this patent UNITED STATES PATENTS539,015 Fontneau May 7, 1895 1,890,581 Kohler Dec. 13, 1932 2,434,935Kroon Jan. 27, 1948 2,445,154 Reed July 13, 1948 FOREIGN PATENTS 976,790France Nov. 1, 1950

